Energy harvesting has received attention in recent years. The energy harvesting is a technology of converting environmental energy such as heat, vibration, light and electromagnetic wave into electric power. As a technology concerning the energy harvesting, there exist in the prior art some thermoelectric generators of generating electric power from thermal energy by means of thermoelectric conversion module (See, Patent Documents 1-3).
According to the conventional thermoelectric generators, on electric power generation, it is necessary to cause a certain amount of temperature difference between both sides of the thermoelectric conversion module by supplying heat to one side thereof by means of a source of heating and releasing heat from the other side thereof by means of a source of cooling. Namely, in the conventional thermoelectric generators, an installation site of the thermoelectric generator is restricted because temperature difference between the source of heating and the source of cooling which are located adjacent to each other is used for electric power generation.
On the other hand, in micropower electronics such as a wireless sensor, a remote monitor and so on, for convenience of maintenance, it is desirable to use environmental energy as a power source instead of commercial power supply or a battery. Therefore, it may be suggested to incorporate the above-mentioned thermoelectric generator as a power source to those micropower electronics. However, there arises a problem that the micropower electronics cannot be freely installed at a place where they are required because of the above-mentioned restriction of installation site of the thermoelectric generators.
A solar cell converting solar light to electricity is also well known as a technology utilizing environmental energy in the prior art. However, according to the solar cell, the electric power generation cannot be conducted after dark, and the production of electricity is not stabilized because sunshine is significantly affected by weather and clouds, so that an electric storage device is required. Consequently, the solar cell is only used as an auxiliary power unit.